Bear came to Sodor on trial with an associate of his, D199. At the time, Bear had no name, only a number: Diesel 7101. However, when Diesel 199 was rude, Bear put him in his place and tried to be respectful to the engines of the North Western Railway. Later, Henry rescued both Bear and Diesel 199 from some technical malfunctions from both parties. Bear learned a great deal from this experience, seeing steam engines as hard-working, resilient, utterly inspirational. Henry put in a good word for Bear, and he joined the railway. The name "Bear" had stuck, due to the loud growls his engine made.
Becoming part of a larger "family", Bear underwent a remarkable attitude shift. Later, trying to be helpful, Bear set off to rescue Henry when his fire bars collapsed, but pretended to require assistance just so Fergus would be dispatched to help. Fergus was overjoyed to work on the Main Line and feel needed, but later on, Fergus discovered that this was all a lie. Feeling betrayed, Fergus stormed away from the yard, leaving Bear feeling very guilty. Derek then told him he still had a little bit to learn about what being a part of a family really meant
He was spotted shunting during Munitions.
That winter, Bear was sleeping with the other diesels, when his growling woke them all up. They all, except Derek, angrily told him off. Trying to be optimistic, he made his way to the station to collect his coaches. Derek followed him and tried to comfort him, but Bear is not only upset about what the diesels said; he is still guilty about what he did to Fergus that summer. Derek tried to cheer him up, but Bear was still upset, until he was put up to the task of taking the passengers to a safer place, away from a nasty blizzard. However, on the way, he got stuck in the snow. Fergus was the only engine available, so he took Jack to help Bear. Fergus was surprised to find the Hymek diesel asleep under the snow. Once he woke up, Bear apologized to Fergus, and the traction engine graciously forgave him, relieving Bear of a great weight on his buffers.
When the Great Waterton tram-line needed repairs, Bear was sent in to help. Unfortunately for him, Charlie was going on an increasingly desperate joking spree to get Molly to laugh, and Bear became the center of what could easily be deemed as Charlie's worst pun line. A single growl was enough to get Charlie to shut-up, and as Bear left, said that Charlie's jokes had the wit and charm of a gluten-free muffin.
Bear is a friendly diesel, with an upbeat attitude. Before he came to Sodor, he was very reserved, but when Henry put in a good word for him, life on the North Western Railway had a strong effect on the good-natured diesel. Bear loves feeling like he's part of a larger family, and goes out of his way to make that possible, even if sometimes it disturbs others! This sometimes lands him into trouble, but he has the best possible intentions!
- Season 0: Old Groaner (does not speak)
- Season 2: Rock-Star (cameo), Pummeling Percy (cameo), Tag-Team, Munitions (cameo), Hibernation, Aura of Menace (indirectly mentioned)
- Season 3: Culdee Fell (cameo), Penn Pals, Ice Breaker, Percy and Asbestos (cameo)
- Web Clips: Walter Sliggs - Meet the Characters! (cameo)